Known in the art are compositions for preventing deposition of inorganic salts comprising aminomethylenephosphonic compounds and surfactant additives. Thus, U.S. Pat. No. 3,467,192 Cl. 166-279 (1968) teaches the use, as the aminomethylenephosphonic compound, of nitrilotrimethylenephosphonic acid of the formula: ##STR3## and as the surfactant--a compound of the formula: ##STR4##
Also known in the art is a composition for preventing deposition of inorganic salts comprising polyethylenepolyamine-N-methylenephosphonic acid of the general formula: ##STR5## wherein n=1 to 14 and polyacrylamide (cf. U.S. Pat. No. 3,483,925 Cl. 166-279, 1968).
Furthermore, also known in the art is a process for preventing deposition of inorganic salts with the use of an aminomethylenephosphonic acid for the general formula: ##STR6## wherein n=1 to 5, (cf. USSR Inventor's Certificate No. 789434, Int. Cl..sup.3 CO2 F 5/14, E 21 B 43/12, 1980).
However, the above-discussed processes provide but an insufficient protective effect against deposition of inorganic salts. Furthermore, the use of polyacrylamide in the above-described compositions involves considerable difficulties in the preparation of working solutions of this particular compound from a gel-like commercial product. The manufacture of an aqueous solution of polyacrylamide requires a special equipment which inevitably causes inefficient labour- and power expenditures.
The closest prior art composition most resembling that of the present invention in the subject matter and the effect obtained is a composition for preventing deposition of inorganic salts comprising a phosphonomethylated derivative of 1,3-diaminopropanol-2 of the general formula: ##STR7## wherein n=1 to 5, and also 1,3-diaminopropanol-2 and/or a derivative of 1,3-diaminopropanol-2 of the general formula: ##STR8## wherein n=2 to 5, hydrochloric acid, sodium chloride and water, the components being present in the following proportions, percent by weight:
______________________________________ phosphonomethylated derivative of 1,3-diami- 5.0-20.0 nopropanol-2 of the general formula (I) 1,3-diaminopropanol-2 and/or a deriva- 3.0-7.0 tive of 1,3-diaminopropanol-2 of the gene- ral formula (II) hydrochloric acid 3.0-30.0 sodium chloride 3.0-7.0 water to 100 (cf. USSR Inventor's Certificate No. 834334, Int. Cl..sup.3 E 21 B 43/00, 1981). ______________________________________
However, this composition possesses but an insufficient protective effect against deposition of inorganic salts and is difficult to handle under winter-weather conditions, since the minimum freezing temperature of the composition is -35.degree. C. The latter condition to a considerable extent restricts the possibility for using this composition in regions with arctic climate, or requires the use of costly antifreeze components.